Here's my situation. The block was sent to the machine shop, they bought all ARP fasteners (main bolts, rod bolts, etc.) and did all the machining. I then got the engine back and began assembling it. Now I was about to seal up the bottom end with the oil pan, then I thought "windage tray", only problem is, I have main bolts, not studs. I emailed ARP & they confirmed what I've been reading here that I cannot swap out the bolts for studs without sending the block back for align boring. Since the engine is already partially assembled & painted, that really isn't an option for me.

Obviously I can just scrap the windage tray idea entirely, but I'm here now, so I figure why not install one if I can.

What do you guys think? What are my options here?

Thanks!

You more likely, than not, can get away with swapping the bolts for studs. The fasteners do not locate the caps, or at least shouldn't. Properly done the caps were located in the cap relief (step) of the block. The relief indexes the caps side to side and the flatness of the bottom of the broach and the bottom of the cap establish front to rear tip, not the bolts. Anybody that tries to use the bolts to hold lateral and vertical alignment of parts, doesn't know diddly about bolts. Though the manufacturers have tried this trick with rod bolts for years, that of using a body fit to align the upper and lower halves. It's OK on the street, but when you start pumping up the power and revs you start finding signs that the cap and shank are squirming around. Race engines used dowels to hold alignment and the new fashion even at the OEM is to use a cracked cap so that the features of the failure zone interlock and keep the parts from moving around. That relieves the bolts from a job they never did well and reduces their efforts to simply applying clamping force which is the only thing their good at. Bolts do not like bending moments applied to them, it's a sure way to discover their structural limits real fast.

The thing you need to be careful of is keeping the location and direction the caps the same as they are currently installed. That is mark them 1-2-3-4-5 and which way is the front, often caps come with a cast or engraved arrow for that purpose, if lacking use a dab of paint or permanent marker. Same goes for the bearing inserts, make sure they stay with the cap you found them in. Many cheepo/weepo shops put in oversize bearings intended for an undersize crank, then they hone bore the bearing for alignment and finish size. Not a bad technique, but precludes switching or replacing the insets without rehoning them.

This shouldn't be a problem, otherwise you could never pull the crank for bearing inspection and put it back together, parish the though you mixed those "locater" bolts, and this is done all the time on competition engines without encountering problems that disturb the align boring.